Salicylates and process for their preparation

ABSTRACT

The invention relates to metal salicylates of the formula   &lt;IMAGE&gt; wherein Me is a metal ion of valency n, n is 2, 3 or 4, and each of the rings A and B independently of the other is unsubstituted or substituted by halogen, lower alkyl, lower alkoxy or an  alpha -methylbenzyl radical. The metal salicylates are particularly suitable developers for the color former in pressure-sensitive or heat-sensitive recording materials.

This is a divisional of application Ser. No. 786,458 filed on Oct. 11,1985, now U.S. Pat. No. 4,687,869, issued on Aug. 18, 1987.

The present invention relates to metal salicylates, to a process for thepreparation thereof, and to the use of these compounds inpressure-sensitive and heat-sensitive recording materials. The metalsalicylates have the formula ##STR2## wherein Me is a metal ion ofvalency n,

n is 2, 3 or 4, and

each of the rings A and B independently of the other is unsubstituted orsubstituted by halogen, lower alkyl, lower alkoxy or an α-methylbenzylradical.

The salicylate moieties occurring 2 to 4 times in the above metal saltsmay be identical or different. Preferably they are all identical.

Lower alkyl and lower alkoxy normally denote groups containing 1 to 5,preferably 1 to 3, carbon atoms. Lower alkyl groups may be methyl,ethyl, isopropyl, sec-butyl, tert-butyl, amyl or isoamyl, and loweralkoxy groups may be methoxy, ethoxy, isopropoxy, n-butoxy ortert-butoxy.

Halogen in the definition of formula (1) denotes for example fluorine,iodine, bromine or, preferably, chlorine.

The metal salts of this invention are preferably derived from divalent,trivalent or quadrivalent metals having an atomic weight from 24 to 210,preferably from 26 to 120. Examples of such metals are aluminium,barium, lead, cadmium, calcium, chromium, iron, gallium, cobalt, copper,magnesium, manganese, molybdenum, nickel, mercury, silver, strontium,tantalum, titanium, vanadium, tungsten, zinc, tin and zirconium.Preferred metals are aluminium, titanium, vanadium, tin and, inparticular, zinc. The ##STR3## is preferably para to the ethylidenegroup. The rings A and B are preferably not further substituted. If theydo contain substituents, then they are preferably further substituted byhalogen, methyl, methoxy or α-methylbenzyl. Each benzene ring A and Bmay conveniently contain 1 or 2 additional substituents. Theα-methylbenzyl radical is normally present in the ring B.

Interesting developers which may be used with advantage in the practiceof this invention, and which may be obtained by the methods describedhereinafter, are aluminium salts or, preferably, zinc salts of asubstituted salicyclic acid compound of the formula ##STR4## wherein thering D is unsubstituted or substituted by α-methylbenzyl.

Among the salicylic acid compounds of formula (2), those compounds arepreferred in which the ring D is unsubstituted.

The preferred developer is the zinc salt of5-[α-methyl-4'-(α-methylbenzyl)benzyl]salicylic acid.

The metal compounds of formula (1 ) constitute a novel class of metalsalts which are suitable developers or electron acceptors forelectron-releasing colour formers.

The metal salicylates of formula (1) are prepared by reacting 1 mole ofa salt of an n-valent metal of an inorganic acid or of a lower aliphaticcarboxylic acid with n moles of a salicylic acid compound of the formula##STR5## wherein n, A and B have the given meanings.

The reaction is conveniently carried out in an alkaline solution of thesalicyclic acid compound and preferably in the presence of an alkali,for example a hydroxide, carbonate or bicarbonate of an alkali metal, orammonium hydroxide, ammonium carbonate or ammonium bicarbonate.

The metallisation can be carried out in the temperature range from 10°to 25° C. In certain cases, and especially when using organic aluminiumsalts, it is necessary to carry out the reaction at elevatedtemperature, preferably in the range from 70° to 200° C. However, thereactants can also be reacted in a melt. Suitable fusing assistants arefor example salts of lower fatty acids, e.g. sodium acetate, amides oflower fatty acids, e.g. acetamide, and also urea or thiourea orN-substitution products thereof.

As metal donors it is convenient to use the metal salts of mineral acidsor carboxylic acids of 1 to 6 carbon atoms, in particular sulfates,halides (chlorides), nitrates, formates, acetates, propionates, oxalatesor citrates.

Representative examples of inorganic metal salts are zinc salts such aszinc chloride, zinc sulfate or zinc nitrate, as well as aluminiumsulfate. Examples of organic metal salts are zinc diacetate, zincoxalate, aluminium triisopropylate or aluminium sec-butylate.

Instead of the above zinc salts, it is also possible to use zinc oxideor zinc carbonate, in which case the reaction with the salicylic acid ispreferably carried out in the presence of ammonium formate.

The substituted salicylic acid compounds of formula (3) and thepreparation thereof are novel.

The process for their preparation comprises reacting 1 mole of salicylicacid with at least 1 mole of a 1-phenylethanol of the formula ##STR6##and at least 1 mole of a 1-phenylethanol of the formula ##STR7## inwhich formulae (4) and (5) above the rings A' and B' are unsubstitutedor substituted by halogen, lower alkyl or lower alkoxy.

The ethanol components of formulae (4) and (5) are preferably identical.

Representative examples of suitable 1-phenylethanol components offormulae (4) and (5) are: 1-phenylethanol, 1-tolylethanol,1-xylylethanol or 1-(chlorophenyl)ethanol.

The process for the preparation of the salicylic acid compounds offormula (3) is conveniently carried out in an organic solvent which doesnot participate in the condensation and in the presence of an acidcatalyst, in the temperature range from 20° C. to the reflux temperatureof the reaction medium, preferably from 80° to 150° C. The reaction timedepends on the temperature and is ordinarily from 1/2 hour to 5 hours,preferably from 1 to 3 hours.

Suitable organic solvents employed as reaction medium are cycloaliphaticor, preferably, aromatic hydrocarbons, for example cyclohexane, benzene,toluene or xylene; chlorinated hydrocarbons such as ethylene chloride,tetrachloroethylene, or chlorobenzenes, e.g. chlorobenzene,chlorotoluene or dichlorobenzene; cyclic ethers, e.g. dioxane ortetrahydrofuran; dimethylsulfoxide, or nitriles of aliphaticmonocarboxylic acids, e.g. acetonitrile, propionitrile or butyronitrile.Mixtures of these solvents can also be used. Preferred solvents arechlorobenzene, chlorotoluene and, in particular, toluene.

Suitable acid catalysts are aromatic sulfonic acids, e.g.benzenesulfonic acid, chlorobenzenesulfonic acid, toluenesulfonic acid,chlorotoluenesulfonic acid or xylenesulfonic acid.

Aromatic sulfonic acids which are formed in situ are preferred, withtoluenesulfonic acid being especially preferred. The preparation oftoluenesulfonic acid in situ is described e.g. in Chemical Abstracts,Vol. 79 (1969), 1066228r. p-Toluenesulfonic acid is also preferred. Ifthis last mentioned compound is used, a solvent may be dispensed with.

After the condensation of the salicylic acid with the other startingmaterials of formulae (4) and (5), the substituted salicylic acid offormula (3) can be further used direct for the preparation of the metalsalt of formula (1). It it is desired to isolate the substitutedsalicyclic acid of formula (3), then the acid solution of the reactionproduct is e.g. first neutralised with aqueous sodium hydroxidesolution, and then the neutral solution is acidified with a lowercarboxylic acid or an inorganic acid, whereupon the product precipitatesin the form of an oil and is separated.

A particularly preferred process for the preparation of the metalcompounds of formula (1), wherein Me is the zinc ion, comprises heatingto the boil, in a reaction medium consisting of toluene andtoluenesulfonic acid prepared in situ, about 1 mole, preferably 1.0 to1.2 moles, of salicyclic acid with more than 2 moles of 1-phenylethanoland effecting condensation, under reflux temperature, for 1/2 hour to21/2 hours. The toluene is then removed, the resultant salicylic acidcompound of formula (3) is dissolved in an aqueous solution of sodiumhydroxide, and the alkaline solution is treated with an inorganic zincsalt, preferably zinc chloride, whereupon the zinc salt of thesalicyclic acid compound of formula (3) is isolated.

The metal-free salicylic acid compound can be readily obtained again bydissolving the zinc salt in a polar organic solvent, e.g. acetone, andacidifying the solution with a dilute inorganic acid, e.g. hydrochloricacid.

A meterial advantage of the present invention resides in the featurethat, surprisingly, by suitable choice of starting materials, inparticular salicylic acid and 1-phenylethanol, it is possible to obtaina novel readily accessible ring-substituted salicylic acid compoundinstead of an esterification product of the salicylic acid, the metalsalt, especially the zinc salt, of which compound is an excellent andeconomically interesting developer for colour formers for use inpressure-sensitive as well as heat-sensitive recording materials.

The metal salicylates of the formula (1) are virtually colourless andodourless and react very readily with conventional colour formers, sothat spontaneous stable and non-fading copies are obtained.

The colour formers suitable for use in the recording or copying materialof this invention are known colourless or faintly coloured chromogeniccompounds which, on coming into contact with the metal compounds of theformula (1) become coloured or change colour. It is possible to usecolour formers, or mixtures thereof, which belong to e.g. the classes ofthe azomethines, fluoranes, benzofluoranes, phthalides, azaphthalides,spiropyranes, spirodipyranes, leucoauramines, quinazolines,triarylmethaneleuco dyes, carbazolylmethanes, chromenoindoles, rhodaminelactams, chromenopyrazoles, phenoxazines, phenothiazines, as well aschromeno or chromano colour formers.

Examples of such suitable colour formers are: crystal violet lactone(Registered Trademark), 3,3-(bisaminophenyl)phthalides,3,3-(bis-substituted indolyl)phthalides,3-(aminophenyl)-3-indolylphthalides,3-(aminophenyl)-3-indolylazaphthalides,6-dialkylamino-2-n-octylaminofluoranes,6-dialkylamino-2-arylaminofluoranes, e.g.6-diethylamino-2-(2'-chlorophenylamino)fluorane,6-dibutylamino-2-(2'-chlorophenylamino)fluorane;6-dialkylamino-3-methyl-2-arylaminofluoranes, e.g.2-anilino-3-methyl-6-diethylaminofluorane or2-(2',4'-dimethylanilino)-3-methyl-6-diethylaminofluorane,6-dialkylamino-2- or -3-lower alkylfluoranes,6-dialkylamino-2-dibenzylaminofluoranes,6-pyrrolidino-2-dibenzylaminofluorane, 6-N-cyclohexyl-N-loweralkyl-3-methyl-2-arylaminofluoranes, 6-pyrrolidino-2-arylaminofluoranes,bis(aminophenyl)furyl-, -phenyl- or -carbazolylmethanes,3'-phenyl-7-dialkylamino-2',2'-spirodibenzopyranes,bisdialkylaminobenzhydrolalkyl- or -arylsulfinates,benzoyldialkylaminophenothiazines or benzoyldialkylaminophenoxazines.

The metal salicylates of formula (1) are suitable developers for apressure-sensitive or heat-sensitive recording material which may alsobe a copying material.

A pressure-sensitive material comprises e.g. at least one pair of sheetswhich contain at least one colour former, dissolved in an organicsolvent, and a metal salicylate of formula (1) as developer.

The developer is preferably applied in the form of a layer to the faceof the receiver sheet.

The metal salicylates of formula (1) may be applied by themselves alone,as mixtures or in admixture with known developers. Typical examples ofsuch developers are activated clays such as attapulgite, acid clay,bentonite, montmorillonite, activated clay, e.g. acid-activatedbentonite or montmorillonite, and also zeolith, halloysite, silica,alumina, aluminium sulfate, aluminium phosphate, zinc chloride, zincnitrate, activated kaolin or any clay, or acidic organic compounds, forexample unsubstituted or ring-substituted phenols,3,5-bis(α,α-dimethylbenzyl)salicylic acid,3,5-bis(α-methylbenzyl)salicylic acid, or salicylates and their metalsalts, or an acidic polymer, for example a phenolic polymer, analkylphenolacetylene resin, a maleic acid/rosin resin or a partially orcompletely hydrolysed polymer of maleic acid and styrene, ethylene orvinyl methyl ether, or carboxypolymethylene.

The developers may also be used in admixture with other basically inertor almost inert pigments or with other auxiliaries such as silica gel orUV absorbers, e.g. 2-(2-hydroxyphenyl)benzotriazoles. Examples of suchpigments are: talcum, titanium dioxide, zinc oxide, chalk; clays such askaolin, as well as organic pigments, e.g. urea/formaldehyde condensates(BET surface area: 2-75 m² /g) or melamine/formaldehyde condensates.

The colour former effects a coloured marking at those points where itcomes into contact with the developer. In order to prevent the colourformers contained in the pressure-sensitive recording material frombecoming active prematurely, they are usually separated from thedeveloper. This separation can conveniently be accomplished byincorporating the colour formers in foamlike, spongelike orhoneycomb-like structures. The colour formers are preferablyencapsulated in microcapsules, which can normally be ruptured bypressure.

When the capsules are ruptured by pressure, for example with a pencil,the colour former solution is transferred to an adjacent sheet which iscoated with the metal salicylate of formula (1) and a coloured area isthus produced. This colour results from the dye which is formed andwhich is absorbed in the visible range of the electromagnetic spectrum.

The colour formers are encapsulated preferably in the form of solutionsin organic solvents. Examples of suitable solvents are preferablynon-volatile solvents, for example a polyhalogenated paraffin such aschloroparaffin, or a polyhalogenated diphenyl, such asmonochlorodiphenyl or trichlorodiphenyl, and also tricresyl phosphate,di-n-butyl phthalate, dioctyl phthalate, trichlorobenzene,trichloroethylphosphate, an aromatic ether such as benzylphenyl ether, ahydrocarbon oil such as paraffin or kerosene, an alkylated (e.g withisopropyl, isobutyl, sec- or tert-butyl) derivative of diphenyl,diphenylalkane, naphthalene or terphenyl; dibenzyl toluene, terphenyl,partially hydrogenated terphenyl, a benzylated xylene, or otherchlorinated or hydrogenated, condensed aromatic hydrocarbons. Mixturesof different solvents, especially mixtures of paraffin oils or keroseneand diisopropylnaphthalene or partially hydrogenated terphenyl, areoften used in order to obtain an optimum solubility for the colourformation, a rapid and intense coloration, and a viscosity which isadvantageous for the microencapsulation.

The capsules walls can be formed evenly around the droplets of thecolour former solution by coacervation; and the encapsulating materialcan consist of gelatin and gum arabic, as described e.g. in U.S. Pat.No. 2,800,457. The capsules can also be formed preferably from anaminoplast or a modified aminoplast by polycondensation, as described inBritish patent specifications Nos. 989 264, 1 156 725, 1 301 052 and 1355 124. Also suitable are microcapsules which are formed by interfacialpolymerisation, e.g. capsules formed from polyester, polycarbonate,polysulfonamide, polysulfonate, but in particular from polyamide orpolyurethane.

In combination with the developers, the microcapsules containing thecolour formers can be used for the production of a wide variety of knownkinds of pressure-sensitive copying material. The various systems differsubstantially from one another in the arrangement of the capsules, ofthe colour reactants, i.e. of the developers, and of the support. Apreferred arrangement is that in which the encapsulated colour former isin the form of a layer on the back of a transfer sheet and the developerof formula (1) is in the form of a layer on the face of a receiversheet.

Another arrangement of the components is that wherein the microcapsuleswhich contain the colour former, and the developer, are in or on thesame sheet, in the form of one or more individual layers, or are presentin the paper pulp.

The capsules are preferably secured to the support by means of asuitable adhesive. As paper is the preferred support, these adhesivesare principally paper-coating agents, for example gum arabic, polyvinylalcohol, hydroxymethylcellulose, casein, methyl cellulose, dextrin,starch or starch derivatives or polymer latices. These latter are e.g.butadiene/styrene copolymers or acrylic homopolymers or copolymers.

The paper employed comprises not only normal paper made from cellulosefibres, but also paper in which the cellulose fibres are replaced(partially or completely) by synthetic polymers.

The metal compounds of formula (1) can also be employed as developers ina thermoreactive recording material. This recording material usuallycontains at least one carrier, one colour former, one developer, andoptionally also a binder and/or wax.

Thermoreactive recording systems comprise, for example, heat-sensitiverecording or copying materials or papers. These systems are used e.g.for recording information, for example in electronic computers,teleprinters or telewriters, or in recording and measuring instruments,e.g. electrocardiographs. The image (mark) information can also beeffected manually with a heated pen. Laser beams can also be used toproduce heat-induced marks.

The thermoreactive recording material can be composed such that thecolour former is dispersed or dissolved in one binder layer and thedeveloper is dissolved or dispersed in the binder in a second layer.

Another possibility comprises dispersing both the colour former and thedeveloper in one layer. By means of heat the binder is softened atspecific areas and the colour former comes into contact with thedeveloper (electron acceptor) at those points where heat is applied andthe desired colour develops at once.

Known developers for this purpose are the same developers as are used inpressure-sensitive papers, and also phenolic compounds, for example4-tert-butylphenol, 4-phenylphenol, methylene bis-(2-methylphenol),4-hydroxydiphenyl ether, α-naphthol, β-naphthol, methyl, ethyl, n-butylor benzyl 4-hydroxybenzoate, 4-hydroxyacetophenone,2,2'-dihydroxydiphenyl, 4,4'-isopropylidenediphenol,4,4'-isopropylidene-bis(2-methylphenol), 4-hydroxydiphenylsulfone,4'-methyl-4-hydroxydiphenylsulfone, 2,4-dihydroxydiphenylsulfone,4,4'-bis(hydroxyphenyl) valeric acid, 2,4-dihydroxybenzophenone,hydroquinone, pyrogallol, phloroglucinol, p-, m- and o-hydroxybenzoicacid, gallic acid, 1-hydroxy-2-naphthoic acid, as well as boric acid ororganic, preferably aliphatic, dicarboxylic acids, for example tartaricacid, oxalic acid, maleic acid, citric acid, citraconic acid or succinicacid.

Fusible, film-forming binders are preferably used for the manufacture ofthe thermoreactive recording material. These binders are normallywater-soluble, whereas the colour formers and the developer areinsoluble in water. The binder should be able to disperse and fix thecolour former and the developer at room temperature.

By applying heat the binder softens or melts, so that the colour formercomes in contact with the developer and a colour is able to form.Examples of binders which are soluble, or at least swellable, in waterare e.g. hydrophilic polymers, for example polyvinyl alcohol,polyacrylic acid, hydroxyethylcellulose, methyl cellulose,carboxmethylcellulose, polyacrylamide, polyvinyl pyrrolidone, gelatin,starch, or etherified corn starch.

If the colour former and the developer are in two separate layers, it ispossible to use water-insoluble binders, i.e. binders which are solublein non-polar or only weakly polar solvents, for example natural rubber,synthetic rubber, chlorinated rubber, alkyd resins, polystyrene,styrene/butadiene copolymers, polymethylacrylates, ethyl cellulose,nitrocellulose or polyvinyl carbazole. The preferred arrangement,however, is that in which the colour former and the developer arecontained in one layer in a water-soluble binder.

The thermoreactive coatings may contain further auxiliaries. To improvethe degree of whiteness, to facilitate the printing of papers, and toprevent the heated pen from sticking, the coatings may contain e.g.talcum, titanium dioxide, zinc oxide, aluminium oxide, aluminiumhydroxide, calcium carbonate (e.g. chalk), clays or also organicpigments, for example urea/formaldehyde or melamine/formaldehydepolymers. In order to effect the colour formation only within a limitedtemperature range, it is possible to add substances such as urea,thiourea, diphenyl thiourea, acetamide, acetanilide, stearylamide,dimethyl terephthalate, phthalic anhydride, metal chlorides, metalstearates, e.g. zinc stereate, phthalonitrile or other appropriatefusible products which induce the simultaneous melting of the colourformer and the developer. Thermographic recording materials preferablycontain waxes, e.g. carnauba wax, montan wax, paraffin wax, polyethylenewax, condensates of higher fatty acid amides and formaldehyde, orcondensates of higher fatty acids and ethylenediamine.

The invention is illustrated by the following Preparatory and UseExamples, in which parts and percentages are by weight, unless otherwiseindicated.

PREPARATORY EXAMPLES Examples 1

250 g of toluene are heated under reflux. Then 7.3 g of 96% sulfuricacid are added dropwise over 50 to 60 minutes and the water formed isremoved as an azeotrope. The mixture is then cooled to 60° C. and 250 gof 1-phenylethanol and 155 g of salicylic acid are added. The mixture isheated to reflux temperature and the water formed during thecondensation is continuously removed as an azeotrope. The toluene isthen removed by distillation and the residue is stirred in 1190 ml of anaqueous 1N sodium hydroxide solution. The resultant solution is allowedto stand for several hours at room temperature, after which time the oilthat has formed on the surface is separated. The residual solution isthen added dropwise, with efficient stirring, at 10°-15° C. to asolution of 200 g of zinc chloride in 600 ml of water. The whiteprecipitate is isolated by filtration and dissolved in 1 kg of toluene.The toluene solution is concentrated by evaporation at 60° C. underreduced pressure, affording 233 g of an anhydrous powder, which is thezinc salt of the formula ##STR8## with a melting point of 130°-190° C.

    ______________________________________                                        Elemental analysis:                                                           ______________________________________                                        cal.  C = 73.06% H = 5.6%   O = 12.7%                                                                             Zn = 8.64%                                found C = 71.8%  H = 5.7%   O = 12.8%                                                                             Zn = 9.7%                                 ______________________________________                                    

Example 2

To a solution of 15.12 g of the zinc salt of formula (11) obtained inExample 1 in 110 ml of acetone are added 50 ml of an aqueous 1Nhydrochloric acid solution. The acid solution is then kept for 1 hour atreflux temperature and subsequently concentrated by evaporation invacuo. The residue is taken up in 80 ml of toluene, whereupon 2 phasesform. The toluene phase is separated and concentrated by evaporation invacuo, affording 13.1 g of a viscous product which is the salicylic acidcompound of formula

    ______________________________________                                         ##STR9##                     (12)                                            Elemental analysis:                                                           ______________________________________                                        cal.         C = 79.74% H = 6.4%                                              found        C = 80.6%  H = 6.8%                                              ______________________________________                                    

Example 3

160 g of o-chlorotoluene are heated to 110° C. Then 3.65 g of 96%sulfuric acid are added dropwise over 35 minutes and the water formed isremoved under reduced pressure. After cooling to 60° C., 125 g of1-phenylethanol and 77.5 g of salicylic acid are added. The mixture isheated to 83° C. and the water formed during the condensation iscontinuously removed as an azeotrope under reduced pressure. Theo-chlorotoluene is then distilled off and the residue is stirred in 560ml of an aqueous 1N sodium hydroxide solution and then diluted with 1liter of water. The resultant solution is left to stand for severalhours at room temperature, after which time the oil that has formed onthe surface is separated. The residual solution is then added dropwiseat 10°-15° C. to a stirred solution of 47.7 g of zinc chloride in 300 mlof water. The precipitate is isolated by filtration, squeezed out, andthe moist filter cake is suspended in 1 liter of water. The suspensionis filtered and the filter cake is again squeezed out and then dried invacuo at 100° C., affording 117 g of a powder with a melting range ofabout 135°-170° C. This product corresponds to the formula (11) inExample 1.

    ______________________________________                                        Elemental analysis:                                                           ______________________________________                                        cal.  C = 73.06% H = 5.6%  Zn = 8.64%                                                                             O = 12.69%                                found C = 71.8%  H = 5.7%  Zn = 8.54%                                                                             O = 12.35%                                ______________________________________                                    

Example 4

With stirring, 465 g of salicylic acid, 735 g of 1-phenylethanol and 36g of p-toluenesulfonic acid.1H₂ O are condensed for 3 hours at 120° C.The water formed during the condensation is continuously distilled off,with further distillation being effected for 30 minutes under reducedpressure after 3 hours. After cooling to 90° C., 1770 ml of an aqueous2N sodium hydroxide solution are added and the resultant solution isthen left to stand for several hours at room temperature. The oil thathas formed on the surface is separated and the residual solution is thenadded at 10°-15° C. to a stirred solution of 290 g of zinc chloride in 4liters of water. The white precipitate is isolated by filtration andsqueezed out. The moist filter cake is suspended in 5 liters of waterand the suspension is filtered. The filter cake is again squeezed outand then dried in vacuo at 50°-70° C., affording 965 g of a powder witha melting range of 105°-140° C. This product contains 95% of the zincsalicylate of the formula (11) of Example 1 and 5% of the zincsalicylate of the formula

    ______________________________________                                         ##STR10##                    (13)                                            Elemental analysis:                                                           ______________________________________                                        cal.  C = 73.06% H = 5.0%  Zn = 8.64%                                                                             O = 12.69%                                found C = 74.1%  H = 5.7%  Zn = 7.67%                                                                             O = 12.4%                                 ______________________________________                                    

Example 5

With stirring, 77.5 g of salicylic acid, 125 g of 1-phenylthanol and 6 gof p-toluenesulfonic acid.2H₂ O are condensed for 3 hours at 120° C. Thewater formed during the condensation is continuously distilled off, withfurther distillation being effected for 15 minutes under reducedpressure after 3 hours. After cooling to 90° C., 295 ml of an aqueous 2Nsodium hydroxide solution are added and the resultant solution is thenleft to stand for several hours at room temperature. The oil that hasformed on the surface is separated and the residual solution is thenadded at 10°-15° C. to a stirred solution of 36 g of Al₂ (SO₄)₃.18H₂ Oin 200 ml of water. The white precipitate is isolated by filtration andsqueezed out. The moist filter cake is suspended in 400 ml of water andthe suspension is filtered. The filter cake is again squeezed out andthen dried in vacuo at 50°-70° C., affording 149.5 g of a powder whichis the aluminium salt of the formula

    ______________________________________                                         ##STR11##                    (14)                                            Elemental analysis:                                                           ______________________________________                                        cal.  C = 77.88% H = 5.97% Al = 2.53%                                                                             O = 13.54%                                found C = 77.6%  H = 6.15% Al = 2.04%                                                                             O = 14.2%                                 ______________________________________                                    

The product additionally contains 0.9% of H₂ O.

Example 6

With stirring, 38.75 g of salicylic acid, 78.3 g of1-(2'-chlorophenyl)ethanol and 3 g of p-toluenesulfonic acid.2H₂ O arecondensed for 3 hours at 120° C. The water formed during thecondensation is continuously distilled off, with further distillationbeing effected for 15 minutes under reduced pressure after 3 hours.After cooling to 90° C., 147.5 ml of an aqueous 2N sodium hydroxidesolution are added and the resultant solution is then left to stand forseveral hours at room temperature. The oil that has formed as lowerphase is separated and the residual solution is then added at 10°-15° C.to an efficiently stirred solution of 24 g of zinc chloride in 200 ml ofwater. The precipitate is isolated by filtration and squeezed out. Themoist filter cake is suspended in 400 ml of water and the suspension isfiltered. The filter cake is again squeezed out and then dried in vacuoat 20° C., affording 70.4 g of a powder of the formula ##STR12## with amelting range of 84°-98° C.

    ______________________________________                                        Elemental analysis:                                                           ______________________________________                                        cal.  C = 61.20% H = 4.23% Cl = 15.36%                                                                            Zn = 7.31%                                found C = 60.4%  H = 4.23% Cl = 15.82%                                                                            Zn = 7.11%                                ______________________________________                                    

Example 7

With stirring, 77.5 g of salicylic acid, 104.4 g of 1-(p-tolyl)ethanoland 6 g of p-toluenesulfonic acid.1H₂ O are condensed for 3 hours at120° C. The water formed during the condensation is continuouslydistilled off, with further distillation being effected for 15 minutesunder reduced pressure after 3 hours. After cooling to 90° C., 295 ml ofan aqueous 2N sodium hydroxide solution are added and the resultantsolution is then left to stand for several hours at room temperature.The solid by-product that has formed on the surface is removed byfiltration and the residual solution is then added at 10°-15° C. to anefficiently stirred solution of 50.3 g of zinc chloride in 400 ml ofwater. The precipitate is isolated by filtration and squeezed out. Themoist filter cake is suspended in 400 ml of water and the suspension isfiltered. The filter cake is again squeezed out and then dried in vacuoat 50°-70° C., affording 149.4 g of a powder of the formula ##STR13##with a melting range of 100°-170° C.

USE EXAMPLES Example 1 Pressure-sensitive recording system

A finely ground aqueous dispersion (2-4 μm) having a 38% solids contentand comprising

1 part of the zinc salt of formula (11) obtained in Example 1,

13 parts of China clay

0.75 parts of a naphthalenesulfonic acid/formaldehyde condensate, and

1.5 parts of a styrene/butadiene copolymer (100%),

is applied with a doctor blade to coated paper having a weight of 48g/m². Coating weight (dry): 6-7 g/m².

The paper coated with the above receiver layer is placed on a sheet ofconventional copying paper (e.g. Zanders) carrying the donor layer, withthe coated sides face to face. The donor layer contains a solution ofthe colour former, e.g. crystal violet lactone, in microcapsules. Anintense blue copy is formed after writing by hand or typewriter.

Example 2

A finely ground aqueous dispersion (2-4 μm) having a 38% solids contentand comprising

1 part of the aluminium salt of formula (14) obtained in Example 5,

6.5 parts of China clay

0.4 part of a naphthalenesulfonic acid/formaldehyde condensate, and

0.7 part of a styrene/butadiene copolymer (100%),

is applied with a doctor blade to coated paper having a weight of 48g/m². Coating weight (dry): 4-6 g/m².

The paper coated with the above receiver layer is placed on a sheet ofconventional copying paper (e.g. Zanders) carrying the donor layer, withthe coated sides face to face. The donor layer contains a solution ofthe colour former, e.g. crystal violet lactone, in microcapsules. Anintense blue copy is formed after writing by hand or typewriter.

Comparably good results are obtained by using the zinc salts of Examples3, 4, 6 and 7 as colour formers instead of the aluminium salt of formula(14).

Example 3 Thermographic recording paper

Two dispersions A and B are first prepared. Dispersion A is prepared bygrinding

8 g of the zinc salt of formula (11) prepared in Example (1),

28 g of a 10% aqueous solution of polyvinyl alcohol 25/140, and

24 g of water,

in a ball mill to a particle size of 2-4 μm, over 3 to 6 hours.

Dispersion B is prepared by grinding

1 g of crystal violet lactone,

3.5 g of a 10% aqueous solution of polyvinyl alcohol 25/140, and

4 g of water,

in a ball mill to a particle size of 2-4 μm.

The two dispersions are then mixed.

The colourless mixture is coated with a doctor blade on paper having aweight of 50 g/m². The coating weight of the mixture is 3 g/m³ (dryweight). The thermographic recording paper so obtained has a colourlesssurface. A blue color develops rapidly at 125° C., with saturation beingreached at 220° C.

Intense blue copies are also obtained by using the metal salicylatesobtained in Examples 2 to 7.

Example 4 Thermotransfer

(a) Preparation of an image transfer sheet A-1

A finely ground dispersion (2-4 μm) of the composition:

10 g of carnauba wax

20 g of crystal violet lactone

5 g of ethyl cellulose

100 g of water

is applied with a doctor blade to paper having a weight of 50 g/m².Coating weight: 7 g/m².

(b) Preparation of a receiver sheet B-1

A finely ground dispersion (2-4 μm) of the composition:

20 g of the zinc salt of Example 4

10 g of powdered silica

30 g of a 10% aqueous solution of polyvinyl alcohol

70 g of water

is applied with a doctor blade to paper having a weight of 50 g/m².Coating weight: 4-5 g/m².

The image transfer sheet A-1 is placed on the receiver sheet B-1, withthe coated sides face to face. Heat is applied to the back of the imagetransfer sheet for 0.3 seconds by a thermoprinter, resulting in theformation of intense blue prints from 170° C. on the receiver sheet B-1.

Intense blue prints are also obtained by using the metal salts ofExamples 1 to 3 and 5 to 7.

Example 5 Pressure-sensitive recording system

A finely ground aqueous dispersion (2-4 μm) having a 38% solids contentand comprising

1 part of a mixture of the zinc salt of formula (11) obtained in Example1, and the zinc salt of 3,5-bis(α-methylbenzyl)salicylic acid in theratio 1:1,

7.4 parts of China clay

0.8 part of a naphthalenesulfonic acid/formaldehyde condensate, and

0.9 part of a styrene/butadiene copolymer (100%),

is applied with a doctor blade to coated paper having a weight of 48g/m². Coating weight (dry)- 6-7 g/m².

The paper coated with the above receiver layer is placed on a sheet ofconventional copying paper (e.g. Zanders) carrying the donor layer, withthe coated sides face to face. The donor layer contains a solution ofthe colour former, e.g. crystal violet lactone, in microcapsules. Anintense blue copy is formed after writing by hand or typewriter.

What is claimed is:
 1. A salicylic acid compound of the formula##STR14## wherein each of the rings A and B independently of the otheris unsubstituted or substituted by halogen, lower alkyl, lower alkoxy oran α-methylbenzyl radical.
 2. A process for the preparation of asalicylic acid compound of the formula (3) ##STR15## wherein each of therings A and B independently of the other is unsubstituted or substitutedby halogen, lower alkyl, lower alkoxy or an α-methylbenzyl radical,which comprises reacting 1 mole of salicylic acid with at least 1 moleof a 1-phenylethanol of the formula ##STR16## and at least 1 mole of a1-phenylethanol of the formula ##STR17## in the presence of an aromaticsulfonic acid, wherein in formulae (4) and (5) the rings A' and B' areunsubstituted or substituted by halogen, lower alkyl or lower alkoxy. 3.A process according to claim 2, wherein the reaction is carried out inthe presence of p-toluenesulfonic acid.
 4. A process according to claim2, which comprises using an aromatic sulfonic acid which is prepared insitu.
 5. A process according to claim 4, wherein the aromatic sulfonicprepared in situ is toluenesulfonic acid.